The research proposed centers around the control by estrogen of genetic transcription and translation in the uterus of the ovariectomized rat and the liver of the male African Clawed Frog, Xenopus laevis. These are two well-known model systems for the study of regulation of synthesis of specific proteins in target tissues. The male frog liver is particularly attractive as a model system. In the absence of estrogen the vitellogenin gene is essentially repressed or completely inactive. Following treatment with estradiol-17-beta, the gene is activated and yolk protein is secreted in prodigious amounts into the blood. Under chronic treatment with estrogen the cells of the male frog liver are specialized to a state wherein 70-80% of the total messenger synthesized is vitellogenin mRNA. Also, an in vitro system is now available for the stimulation by estrogen of cultured liver explants. These two model systems will be exploited for the following major specific aims: (1) to determine the ontogeny of the capacity of estrogen to evoke vitellogenin synthesis in hepatic tissue of Xenopus at various stages of development; (2) to determine the amounts of specific estrogen-binding protein (receptor) in Xenopus liver, and whether these levels correlate with the degree of estrogen-induced vitellogenin synthesis observed during ontogeny of this hormonal response system; (3) to further identify, characterize, and delineate the sequential appearance of estrogen-induced nonhistone chromosomal proteins, as a function of time after treatment with estradiol-17-beta, in both the rat uterus and the Xenopus liver (this work will employ recently developed refinements in methodology, the O'Farrell method of two-dimensional electrophoresis, to extend our earlier studies and knowledge of the qualitative and quantitative changes in these estrogen-induced proteins; (4) to investigate the mechanism underlying the estrogen "memory response" observed in liver of adult male Xenopus during secondary hormonal stimulation (this work will involve testing the hypothesis that specific nonhistone chromosomal proteins are responsible for the "memory response"); (5) to attempt to purify the nuclear form of the estrogen receptor from hepatic tissue of male Xenopus, with the hope of obtaining an assay for the estrogen-receptor protein itself.